Lawyers for millionaire murder suspect Robert Durst filed a motion Wednesday to get his arrest on gun and drug charges in Louisiana thrown out, arguing FBI agents illegally searched his hotel room and police then tried to cover up the violation.

The LAPD has charged Durst — the subject of the HBO documentary series "The Jinx" — with the 2000 murder of his Beverly Hills confidant, Susan Berman. But some legal experts think the lesser charges based on what was found at the J.W. Marriott in New Orleans could pose a bigger threat to the real-estate scion because they are easier to prove.

Defense lawyers want to take Durst back to California. They argued the Louisiana case should be quashed on technicalities.

The lawyers allege that when the FBI detained Durst in the hotel lobby on March 15, no search warrant for his room was in effect — yet agents rummaged through and photographed his belongings, finding the .38 caliber revolver and almost 150 grams of pot. They scoffed at the claim that the FBI search was an inventory for safekeeping.

"Mr. Durst's hotel room was secure and paid for, Mr. Durst was safely in custody, and there was no contraband in plain view," they wrote. "The FBI agents could have simply closed the door and left, and there was no need for the FBI to ensure 'safekeeping' of Mr. Durst's belongings."

The LAPD did not apply for a Louisiana search warrant until hours later and did not tell the court that the room had already been searched for the FBI, Durst's attorneys said. And when Louisiana police applied for an arrest warrant for Durst, they said the gun and drugs were seized after the LAPD had obtained the search warrant, the motion states.

The motion was filed a day before Durst was set to appear in a New Orleans courtroom for a preliminary hearing. He has denied killing Berman.

IN-DEPTH

Rappleye is a reporter with the Investigative Unit at NBC News, covering immigration, criminal justice and human rights issues.

Tracy Connor

Tracy Connor is a senior writer for NBC News. She started this role in December, 2012. Connor is responsible for reporting and writing breaking news, features and enterprise stories for NBCNews.com. Connor joined NBC News from the New York Daily News, where she was a senior writer covering a broad range of news and supervising the health and immigration beats. Prior to that she was an assistant city editor who oversaw breaking news and the courts and entertainment beats.

Earlier, Connor was a staff writer at the New York Post, United Press International and Brooklyn Paper Publications.

Connor has won numerous awards from journalism organizations including the Deadline Club and the New York Press Club.